Introduction

Sigma lately had quite a run in delivering very decent products not only in terms of value but also optical and mechanical quality as well as improved quality control. The transformation of their product lineup is still in the early phase, but they are busy executing their new product vision.

One of their latest products is the Sigma 24-105mm f/4 HSM DG OS | A. As the name implies, it is part of the "Art" series, thus their most prestigious segment of lenses. In Nikon land, it obviously targets the Nikkor AF-S 24-120mm f/4 VR, which so far has been the only real option option for customers looking for a high quality, full format standard zoom lens with a slightly longer reach.

Interestingly the Sigma lens is just slightly more affordable than its Nikon counterpart. This certainly shows that Sigma is getting more confident about its products compared to high end products from original manufacturers.

The build quality of the Sigma lens is - although it may still be surprising for some - simply superb. Besides some metal parts, Sigma uses a new material called TSC (Thermally Stable Composite) which contributes to the high quality perception. There's no wobbling whatsoever and that's despite a duo-cam zooming mechanism (two inner lens tubes).

The broad zoom and focus rings are nicely rubberized and operated smoothly.

It is worth to mention that the lens is rather massive especially when zooming towards the 105mm setting and with attached lens hood.

You've probably read it here before, but we still feel the need to hint at it: the zoom and focus ring rotates in "Canon" style, which is the exact opposite of how focus things work on Nikkor lenses. So, if you're used to the Nikon way of zooming and manual focusing, the Sigma lens may be a challenge for your muscle memory. And you'll also have to remember that the focus assist in the viewfinder assumes a Nikon lens and consequently suggest the wrong direction of focus ring movement.

The lens features HSM, which is Sigma's version of ultra-sonic drive. Thanks to that, the lens is fully compatible with all current Nikon DSLRs, including the entry-level DX models. Typical for many HSM lenses, the AF is virtually silent and very fast.

Image stabilizers are mainstream theses days and Sigma has implemented their variant (OS="Optical Image Stabilizer") which provides an equivalent gain of around 3 f-stops in real life situations.

It is also worth to note that the lens is compatible to Sigma's USB dock (for AF/OS tuning) and they also offer a mount conversion service (e.g. Nikon to Canon EF).